An increasing number of technologies require integration of disparate classes of separately fabricated objects into spatially organized, functional systems. Examples of systems that rely critically on heterogeneous integration range from optoelectronic systems that integrate lasers, lenses and optical fibers with control electronics, to tools for neurological study that involve cells interfaced to arrays of inorganic sensors, to flexible circuits and actuators that combine inorganic device components with thin plastic substrates. The most significant challenges associated with realizing these types of systems derive from the disparate nature of the materials and the often vastly different techniques needed to process them into devices. As a result, all broadly useful integration strategies begin with independent fabrication of components followed by assembly onto a device substrate.
As one example of an integration strategy, Laser Direct-Write (LDW) processing techniques have been succinctly categorized by Arnold and Pique [1]. Some of the present methods fall within the LDW category referred to as Laser Direct-Write Addition (or LDW+) and, more specifically, Laser-Induced Forward Transfer (LIFT) or Laser-Driven Release. This type of a transfer process was first reported by Bohandy et al [2]. LIFT-type processes have been used, for example, to assemble or print fabricated microstructures, and Holmes and Saidam [3], calling the approach Laser-Driven Release, used it for batch assembly in microelectromechanical system (MEMS) fabrication.
Most LDW processes involve ablation of a sacrificial layer that holds an object to a transfer surface. During transfer, the sacrificial layer is vaporized to form a gas that expels the object from the transfer surface to a receiving substrate. However, these processes suffer from time- and material-related expenses resulting from the necessity of forming and then destroying the sacrificial layer. They also risk contamination of the final product due to the ubiquitous presence of the ablated sacrificial material.
A number of patent and non-patent documents describe methods and systems for transfer printing, including U.S. Pat. Pub. No. 2009/0217517; U.S. Pat. Nos. 7,998,528; 7,932,123; and 7,622,367; Holmes et al., “Sacrificial layer process with laser-driven release for batch assembly operations,” J. MEMS, 7(4), 416-422, (1998); and Germain et al., “Electrodes for microfluidic devices produced by laser induced forward transfer,” Applied Surface Science, 253, 8328-8333, (2007), each of which is hereby incorporated by reference to the extent not inconsistent herewith.